The subject of the present invention is a resonant device comprising a mass/spring system associating a main mass and a spring, usable as a passive or active striker tuned in such a way as to stifle a vibration, or else as a generator of dynamic loads so as to apply loads to a structure.
Tuning is obtained by choosing the mass and the stiffness of the spring so that for example the natural frequency of the mass/spring assembly is equal to that of the vibration to be generated or to be stifled.
A match between the device and the vibration or vibrations to be stifled poses a certain number of problems. One of these problems is that, for the known devices, the tuning frequency is fixed, and that the device cannot therefore be used other than for operation at a given frequency.
According to a first aspect, the present invention aims to allow frequency adjustment of the device.
For this purpose, the invention relates to a passive or active resonant device comprising a mass/spring system composed of a main mass comprising at least one main mass element, and of at least one spring element, which device comprises at least one additional mass comprising at least one additional mass element and a coupling device able to couple the additional mass to the main mass and to decouple it therefrom, so as to modify the tuning frequency of the device.
The device can be one which comprises at least one electromagnetic assembly comprising two complementary devices of which the first exhibits at least one electromagnetic piece and of which the second exhibits at least one electromagnet, one of the two complementary devices being coupled to the main mass, and the other complementary device being coupled to an additional mass, the two devices being disposed facing one another, in such a way that, when one said electromagnet is activated, two said complementary devices are mechanically integral, so that the main mass and said additional mass are coupled.
At least one electromagnetic piece can be coupled for example elastically to the main mass, at least one electromagnet then being coupled to said additional mass. Said elastic coupling, which is for example produced with the aid of a flexible leaf, can exhibit an elastic degree of freedom in a direction substantially perpendicular to a main direction of the oscillations of the main mass, for example the direction of generation of loads.
The device can be one wherein a first complementary device comprises two electromagnetic pieces spaced apart form one another and integral with said flexible leaf, and wherein a second complementary device comprises two electromagnets disposed facing the two electromagnetic pieces. The two electromagnets may be integral with at least one linking piece.
At least one additional mass may be held in position by an elastic device which exhibits an elastic degree of freedom in a direction substantially parallel to a main direction of the oscillations of the main mass, this elastic device exhibiting for example at least one elastic leaf.
Another problem with the prior art devices is that, once a frequency has been chosen, it is difficult to control the amplitude of the oscillations of an active striker, also referred to as a generator of dynamic loads, which may, in the vicinity of resonance, become very large and lead to the saturation or even to the destruction of an actuator producing said dynamic loads.
Yet another problem with the prior art devices is that it is difficult to transmit sizable dynamic loads.
According to a second aspect, the present invention allows good control of the amplitude of the oscillations, and/or allows the transmission of sizable loads.
For this purpose, the invention proposes a generator of dynamic loads comprising a main mass/spring system composed of a main mass comprising at least one main mass element of mass m2 and of at least one main mass element of mass m2 and of at least one spring element of stiffness K2, and which is such that it comprises an auxiliary mass/spring system which is coupled to the main mass/spring system and which is composed of an auxiliary mass of mass m3 and of at least one auxiliary spring element of stiffness K3, the assembly exhibiting a first and a second resonant frequency, denoted f6 and f2 respectively, and an anti-resonant frequency f1, with f0 less than f1 less than f2. The generator can in particular operate at the frequency f0 and/or at the frequency f1, for example with the aid of an excitation device for actuating the generator between the frequencies f0 and f2 and in particular at the anti-resonant frequency f1.
In general, the generator can normally operate at any frequency. Its use is not limited to the frequencies f0, f1, f2, but, the characteristic of anti-resonance at the frequency f0 is not utilized.
The benefit of operation at the frequency f1 (or in the vicinity thereof) is that it allows operation at reduced amplitude, so that it is practically impossible to saturate the actuator mechanically, whereas one still benefits from the mechanical amplification. The only limitation being the maximum intensity allowed by the generator, it is possible to generate sizable loads which may be transmitted to a structure.
Moreover, it is possible to vary the aforesaid frequencies and in particular the frequencies f0 and f1, by adding at least one additional mass which can be coupled or decoupled from the main mass, in accordance with the first aspect of the invention, according to the various embodiments mentioned hereinabove.